The invention relates to a radiant heater comprising within an extremely free periphery of a supporting base body of insulating material and/or metal a single or several heating fields. The latter may be located alongside and/or within each other at right angles to a center axis of the base body so that an outer heating field annularly surrounds an inner one partly or totally. Each heating field is assigned heating means such as a heating resistor or heating conductor which in operation thermally radiates in the direction of the front or upper side of the heater, usually through a cover which is permeable to the radiation or translucent, against the rear side of which the base body is in contact by one or more facing surfaces under compressive stress.
Each heating conductor may be disposed as a profile free of contact with the cover or at least partly exposed spaced away from the front side of the base body so that it defines in operation a given visible glow pattern. Connected to its ends and/or spaced between therein each portion of the resistor extending continuously or integrally over the associated length is connected to a connecting conductor, via which the resistor is electrically connected from the outer side of the base body or from a connecting body secured to the latter. This conductor is, like the resistor, not provided with a preassembled sheathing or it is arranged exposed metallically bare on the same front side as the resistor. The connecting wire may be located over its full length within one or more heating fields adjacent to the resistor and may be visible over at least part of this length like the resistor. In this arrangement means are expediently provided which prevent a change in the glow pattern in operation of the connecting wire to the extent that the latter makes no or merely a hardly recognizable contribution to the configuration of the glow pattern. This applies in particular to those portions of the connecting wire which significantly approach from the periphery of a heating field the center thereof, located nearer to a temperature sensor than the resistor arrangement as viewed from the front and/or guided through a heating field or passing near to a heating field into a further heating field. The heating fields are to be operated separately, e.g. so that a central heating field may be operated selectively alone or in combination with an outer defining heating field, to make for one and the same cooking point overall heating fields of differing size available for cooking receptacles of various sizes.
In operation of such a heater the connecting wire is exposed to heating by radiation from the adjacent resistor in each case and thus to alternating elongations which lead to deformations. If the conductor is a straight wire which between its ends is curved only corresponding to the path of the connection, this wire bows in elongation. The conductor becomes all the more deformed, the more it is required to provide a heating output in operation due to an increased inherent resistive value.